This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The main purpose of this study is to compare leg blood flow and vascular conductance responses to submaximal dynamic exercise between older individuals over a broad range of fitness and activity levels. We hypothesize that a) fitness level will have a modulatory influence on the hemodynamic response to graded exercise such that leg blood flow will be higher in more fit older men as compared to less fit older men. Secondly, we hypothesize that a) fitness across a relatively "normal" range will not have a modulatory influence on the hyperemic response to submaximal exercise in older women, and b) older women with the highest fitness levels will show preserved blood flow responses to exercise as compared to young women.